The present invention is related to computer systems, and more particularly, to computer systems specially adapted for executing encrypted program instructions
There are many known techniques for protecting information, whether programs or other kinds of information using encryption. The present invention applies prior art encryption techniques to computer systems in order to provide protection against the unauthorized use of computer programs o software.
It is known that a software supplier can control the use of his software to a certain extent simply by encrypting it and arranging for the operating system, or applications subsystem, of a computer to decrypt the "protected" software prior to execution. However, with this approach, the plaintext version of the program is vulnerable to being copied by relatively trivial circumventions of the operating or application systems
In the prior art, U.S. Pat. No. 4,278,837, discloses a technique of encryption of the program-to-be-protected, of the encrypted program to obtain an executable set of instructions. However, the method of that patent requires a specialized microprocessor chip as the execution engine. Furthermore, the method of that patent exacts a considerable execution performance penalty.
It is an object of the present invention to provide an improved computer system for executing encrypted computer programs.
It is another object to provide a computer system which minimizes the accessibility of plaintext versions of an encrypted program to a user.